FFmpeg,PCM轉(zhuǎn)MP3,編碼器為空是怎么回事,求大哥們教我

/**
 * 音頻編碼
 * @param path PCM文件地址
 * @param out 輸出MP3文件地址
 */
void encoderAudio(const char* path,const char* out){
    //注冊(cè)輸入輸出組件
    av_register_all();
    //第二步：打開輸入音頻文件
    //封裝格式上下文
    AVFormatContext *av_fm_ctx = avformat_alloc_context();
    //輸出流
    AVOutputFormat* ouput_format = av_guess_format(NULL,out,NULL);

    av_fm_ctx->oformat = ouput_format;
    //打開輸出文件
    if (avio_open(&av_fm_ctx->pb,out, AVIO_FLAG_READ_WRITE) < 0){
        LOG_I("Failed to open output file!\n");
        return;
    }

    AVStream* avStream = avformat_new_stream(av_fm_ctx, 0);
    if (avStream==NULL){
        LOG_I("avStream獲取失敗");
        return ;
    }

    AVCodecParameters* av_codec_parameters = avStream->codecpar;
    av_codec_parameters->codec_id = ouput_format->audio_codec;
    av_codec_parameters->codec_type = AVMEDIA_TYPE_AUDIO;
    av_codec_parameters->format = AV_SAMPLE_FMT_S16;
    av_codec_parameters->sample_rate= MAX_AUDIO_FRAME_SIZE;
    av_codec_parameters->channel_layout=AV_CH_LAYOUT_STEREO;
    av_codec_parameters->channels = av_get_channel_layout_nb_channels(av_codec_parameters->channel_layout);
    av_codec_parameters->bit_rate = 64000;
    //打印有關(guān)輸入或輸出格式的詳細(xì)信息
    av_dump_format(av_fm_ctx, 0, out, 1);
    //4.獲取編碼器(根據(jù)編碼器的ID，找到對(duì)應(yīng)的編碼器)
    AVCodec *av_codec = avcodec_find_encoder(av_codec_parameters->codec_id);
    if(av_codec==NULL){
        LOG_I("編碼器生成為空：");
        return;
    }

    //打開編碼器
    AVCodecContext *av_codec_ctx = avcodec_alloc_context3(av_codec);
    //根據(jù)所提供的編碼器的值填充編譯碼上下文
    int avcodec_to_context = avcodec_parameters_to_context(av_codec_ctx,av_codec_parameters);
    if(avcodec_to_context < 0){
        LOG_I("編碼器上下文填充失敗");
        return;
    }
    //打開編碼器
    int av_codec_open_result = avcodec_open2(av_codec_ctx, av_codec, NULL);
    if (av_codec_open_result < 0) {
        LOG_I("編碼器打開失敗!");
        return;
    }


    FILE *pcm_file = fopen(path,"rb");
    if(pcm_file==NULL){
        LOG_I("文件打開失敗");
        return;
    }



//保存一幀讀取的壓縮數(shù)據(jù)-(提供緩沖區(qū))
    AVPacket *packet = (AVPacket *) av_malloc(sizeof(AVPacket));

    //Write Header
    avformat_write_header(av_fm_ctx,NULL);

    //編碼寫入數(shù)據(jù)
    int ret;
    while(fread(packet, 1, (size_t)packet->size, pcm_file)){
        //發(fā)送數(shù)據(jù)包
        avcodec_send_packet(av_codec_ctx, packet);
        //接收數(shù)據(jù)包
        ret =  avcodec_receive_packet(av_codec_ctx,packet);
        if(ret == 0){

            packet->stream_index = avStream->index;

            av_write_frame(av_fm_ctx, packet);
        }

    }
    fclose(pcm_file);
    av_write_trailer(av_fm_ctx);
    avcodec_close(av_codec_ctx);
    avformat_free_context(av_fm_ctx);
    avcodec_free_context(&av_codec_ctx);
    avcodec_parameters_free(&av_codec_parameters);
    av_packet_free(&packet);
    av_freep(ouput_format);
    av_freep(avStream);
}